The present invention relates to equipment for compensating for variations in sensors forming part of measuring apparatus. In particular variations such as temperature variations resulting from changes in the ambient conditions are to be compensated. In this type of apparatus, measurement occurs in a number of measuring cycles and, at the beginning of each measuring cycle, the measurement is carried out with respect to a given reference value. A preferred field of application of the present invention is the compensation of temperature variations of sensor characteristics in injection molding machines.
Quite generally speaking, when measuring any characteristics such as pressure, temperature, torque, etc., changes in sensor characteristics due to changes in ambient conditions result in errors in the measurement. For example, when measuring pressure, changes in temperature can cause errors; in the opposite case, for temperature measurements, changes in pressure can result in the same effect. As a further example, changes in temperature can cause errors when measuring the stress and strain in machine parts by means of strain gauges. The temperature changes also introduce an error when determining the pressure in injection molding machinery. While, in many cases, it is possible to eliminate or decrease the influence of temperature by the use of bridge or other compensating circuits at the place of measurement, this is not always possible. For example, particularly in injection molding machines lack of space at the location of the sensor does not allow the introduction of compensating equipment. Further, such circuits usually operate correctly only within predetermined temperature ranges while temperature changes in excess of the determined temperature range again cause errors in the measurement.